Rising cost in fuels and the potential danger of nuclear reactors have increased the efforts to find an alternative source of energy. One direction being explored is solar energy which can be used to provide illumination and heat. In many states, direct sunlight is available between 2000 and 2500 hours per year. Optimal utilization of available solar energy to commercial buildings can save over 50% of energy costs during daylight hours.
The Solar Energy Research Institute and the Lawrence Berkeley Laboratory, Windows Research Division have been conducting research on the use of solar energy for illuminating the interiors of commercial buildings. One such system under investigation uses a tracking heliostat to reflect light onto a skylight. Another concentrates direct sunlight onto a tubular mirror system for distribution of illumination throughout the building. By combining these two, solar energy becomes competitive.
There are several patents on the subject of solar energy as a source of daylighting in interior of a building. Two such patents are U.S. Pat. Nos. 3,033,144, Nicolson and 4,349,245, Kliman. The Nicolson patent employs a lens system on a rotating tracking system for following the sun and a light conduit with prisoms and lenses for directing daylight in a building. In the Kliman patent, the sun's rays are collected by a heliostat and directed to a dielectric mirror where visible light is reflected through a distribution system to various points of illumination in a a building.
The use of solar energy is also disclosed in the following U.S. patents: U.S. Pat. No. 4,211,212, U.S. Pat. No. 4,282,858, and U.S. Pat. No. 4,335,578.